Japanese researchers randomly selected 28 game videos featuring two university teams and evaluated a total of 3,970 tackles. In about 10 percent of the tackles, the tackler’s head was incorrectly positioned in front of the ball carrier.

World Rugby, the sport’s governing body, says the tackler must be positioned behind or to one side of the ball carrier.

“When we did our own comprehensive head injury study in late 2016, the specialist working group identified technique as a key focus area, and the tackle law amendment in January was aimed at adjusting the technique of the tackler to remove the player from the area of greatest risk,” a World Rugby spokesperson told Reuters Health by email.

Evidence from the 2016 study showed that 76 percent of all head injuries occur in the tackle, and the risk of injury for the tackler is more than two and a half times greater than for the ball-carrier, with tackle height a contributing factor.

In the current study, the incidence of injury was 69.4 per 1,000 tackles when head positioning was incorrect, falling to 2.7 per 1,000 tackles with correct positioning, Dr. Takayuki Kawasaki of the Juntendo University Faculty of Medicine in Bunkyo, Tokyo, and colleagues found.

Injuries were more common when tackles were of shorter duration and when there was shorter distance covered before contact, the researchers wrote in the British Journal of Sports Medicine.

“This particular study supports our evidence-based position that the promotion of correct technique in the tackle has a significant injury-prevention benefits,” the World Rugby spokesperson said.

Despite several interventions to address concussions, neck injuries, pinched nerves and shoulder injuries that commonly result from rugby tackles, including changes in technique and exercises aimed at reducing injury, no formal prevention strategy is in place, the researchers noted.

As part of the study, players who tackled with incorrect head positioning completed a questionnaire, after watching a video of the tackle within a week following the match. Responses showed that in nearly 14 percent of incorrect tackles analyzed, the head positioning was intentional, and 61 percent of players said they could avoid tackling with incorrect positioning.

“With correct coaching and technique, the wide-ranging benefits of involvement in the sport far outweigh the risks,” said Dr. Ian Gibbons, a senior house officer at Royal Surrey County Hospital in Guildford, who played rugby from age four through medical school.

“This study looked at university rugby, where a lot of people may not have had the foundations of sound basic tackling technique from a young age. University rugby can be quite disorganized with extremely variable levels of coaching quality . . . so these are a section of players who would be vulnerable to tackling injuries,” Gibbons, who was not involved in the study, said in an email.

The researchers acknowledge that their small study’s results may not be generalizable to all rugby players. Disparities in the teams’ levels, tactics and coaching methods could also impact the incidence of injury, they added.

Gibbons noted that while players in the UK play in age categories, in New Zealand they are divided into weight categories. “Matching players of the same weight/size at a young age could help ensure a good technique is mastered,” he said.